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5.2 Biotechnology-based Wastewater Treatment

Introduction

Ukrainian Academy of Sciences Institute of Colloid and Water Chemistry, in cooperation with a number of organizations, has developed and implemented a flow-through biotechnology for wastewater treatment that uses a sequence of bacteria and hydrobionts (aquatic fauna) to immobilize contaminant loads. These biotechnologies are widely used in wastewater treatment, drinking water pretreatment, and purification of rainfall and surface waters (in lakes, bays, channels, etc.).

Technical Description

While this technology can be specifically adapted for particular groups of pollutants, this case study will examine the biotechnology proposed for use in the treatment of wastewater from a yeast production facility. This technology includes three stages. In the first stage, the effluent is subjected to anaerobic treatment in three consecutive biological reactors (concrete submerged tanks, filled with "Vija" fibre produced from textured nylon with a specially tailored interlacing). The fibres provide a substrate that approximates sone 10 000 to 100 000 m2 of surface area/m3 of fibre. The anaerobes that inhabit this surface area can reduce the COD of the influent wastewater by not less than 80% (as COD). In the second stage, the effluent is subjected aerobic treatment in a modified trickling biological filter, wherein the conventional substrate of rocks has been replaced by additional fibre batting. In this chamber, the effluent is denitrified to rid the effluent of excess ammonia. In the third stage, the effluent is subjected to aerobic mineralization using activated sludge. This stage serves as a final polishing stage in the enhanced water purification process. When the contaminated water emerges from this portion of the process, its BOD is reduced from 3 000 mg/l to 6 mg/l.

Extent of Use

Table 6 lists the industrial facilities in which biotechnological systems of wastewater treatment are in operation.

Operation and Maintenance

Operation and maintenance costs incurred using this technology are 3 times less than the costs of wastewater treatment in aerobic activated sludge tanks, and half as many staff are required to operate this type of technology. The types of professional skills, however, are slightly different to those required in conventional wastewater treatment plants as one staff member should be a biologist-ecologist (in addition to an engineering technician and electrician). Because this is a biological rather than a mechanical system, electric power consumption is reduced by a factor of 3 times. Likewise, because of the mix of aquatic organisms used in this treatment process, the amount of activated sludge is reduced by 5 times. The microorganisms used in the process could be selected from local sources.

Level of Involvement

This technology is typically implemented by the private sector, when employed in the factory setting, or by the municipal sector, when used for community wastewater treatment.

TABLE 6. Application of Biotechnology-based Wastewater Treatment Systems in Ukraine.

Costs

The capital cost of a biotechnology-based treatment facility with a capacity of 1 500 m3/day is about $2 430 000 (or $1.62 per unit of output). Operation and maintenance costs are 3 times less than the cost of water treatment in aerobic sludge tanks. The fibre batting costs $10/kg. Purification facilities generally use between 0.3 and 3 kg of this material/m3 of effluent treated. In most applications, the depreciated cost of wastewater treatment prior to the introduction of biotechnological-based treatment was $376.10 (or $0.25 per unit of output), and, after its implementation, these costs declined to $150.20 (or $0.10 per unit of output). Under ideal conditions, the biotechnological treatment is self-adjusting once it has been launched.

Effectiveness of the Technology

In urban wastewater treatment applications, these biotechnologies produce an effluent which improves on the performance of conventional biological treatment facilities by 50% to 60% overall. Water quality of the purified water leaving the plant is 5 to 10 times better; typical output has a COD of between 15 and 20 mg/dm³, a BOD of between 2 and 3 mg/ dm³, and a suspended matter concentration of less than 2 mg/dm³.. Power costs are reduced by 3 to 4 times, and surplus sludge quantities are reduced by 5 to 8 times.

Advantages

Under ideal conditions, the treatment facility is self-adjusting, and can be used to purify any wastewater, including almost toxic wastewaters, to required levels of water purity.

Disadvantages

There are no known disadvantages to the use of biotechnology-based wastewater treatment methods.

Further Development of the Technology

This biological technology is based upon universal principles inherent in aquatic ecology. Hence, this type of system can be used for the treatment of both raw water and wastewater from various industrial and municipal sources. The basic principles employed are the principles of spatial succession of different microorganisms and of the nutritional chain of hydrobionts (the food web). The technology is generally reagent-free, but, in the case of the technology being used for water treatment in chemical facilities, reagents might be also used for pretreatment of the wastewater. Reagents may also be used when there might be a shortage of biological growth elements in the water being treated.

In industrial waterworks, this reagent-free, inexpensive, and environmentally-safe treatment method can replace the traditional chemical (biocide) treatment of recycled water needed to reduce biological growth within heat-exchangers. In natural waters, this technology can be used to completely remove up to 100 ml of oil per square meter of water surface daily.

Information Sources

Dr Vladimir A. Demkin, Ministry of Environmental Protection and Nuclear Safety, 5 Khreschatyk St., Kyiv-1, Ukraine, Tel. (380-44) 228 0786, fax: (380-44) 229 8050, e-mail: demkin@mep.freenet.kiev.ua.

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